Increasing Plant Density Research Articles

Times of Trinexapac-ethyl application associated to plant densities in agronomic performance of second-season corn

Plant growth regulators, which can alter the plant size and anatomy, allow the use of cultivars of interest that do not have a modern leaf architecture, making higher plant densities possible. The objective of this study was to evaluate the agronomic performance of second season corn, grown at different plant densities and under Trinexapac-ethyl applications at different stages of crop development. The field study was carried out in two growing seasons (2013 and 2014), at the Fazenda Escola of the State University of Londrina. Fifteen treatments were evaluated in a randomized block, 5 x 3 factorial design, at five plant densities (40,000, 60,000, 80,000, 100,000 and 120,000 plants per hectare), of Trinexapac-ethyl applied in three stages: control (no application), V6 and V9, with four replications. The morphological plant characteristics, the yield components and grain yield were evaluated. Increases in plant density raise the plant height, reduce the number of grains per ear, ear length and 100-kernel weight, and have no influence on grain yield. The application of Trinexapac-ethyl in stage V9 reduces plant and ear insertion height and 100-kernel weight.

Plant density and nitrogen topdressing of high-altitude main-season corn

An appropriate combination of plant density with nitrogen (N) fertilization can optimize corn growth and increase grain yields. This study evaluated the effects of nitrogen topdressing rates and plant density levels on the agronomic performance of corn. The early hybrid DKB 240 YG, with high yield potential and stability, was evaluated in two summer crops in Mauá da Serra, Paraná (950 m asl), in a Cfb climate, on a Rhodic Eutrudox. The experiment was arranged in randomized complete blocks and subdivided plots with four replications. The plant densities (60,000; 75,000; 90,000 and 105,000 plants ha-1) were assessed in the plots and the nitrogen (ammonium nitrate 32% N) topdressing rates (0, 60, 120, 180 and 240 kg ha-1) in the subplots. The stem diameter, plant height, ear insertion height and grain yield were evaluated. The stem diameter, plant height, ear insertion height and grain yield were influenced by the interaction between plant density and nitrogen topdressing under the tested high-altitude edaphoclimatic conditions. The stem diameter of corn plants decreased due to the increase in plant density whereas nitrogen topdressing attenuated this reduction. Maximum plant height was observed at a density of 75,000 plants ha-1 associated with a topdressing of 169 kg ha-1 of N, and highest ear insertion at 60,000 plants ha-1 and 168 kg ha-1 of N. Corn yield was highest at a density of 105,000 plants ha-1 associated with a topdressing of 185 kg N ha-1 of N.

Influence of floating plant density on potential herbicide spray loss.

Mesocosm experiments were conducted to evaluate the effect of floating plant density on over-the-top spray solution loss to the column using a tracer dye. Experiments quantified in-water rhodamine water tracer (RWT) dye concentration after foliar treatment at 935 L ha-1 to waterhyacinth [Eichhornia crassipes (Mart.) Solms], waterlettuce (Pistia stratiotes L.) and giant salvinia (Salvinia molesta D.S. Mitchell) at 0, 25, 50 and 100% area covered (PAC). As expected, spray loss to the water surface decreased with increasing plant density in all species. However, each species exhibited an unique relationship between density and percentage spray loss. The plant material required to result in 50% spray loss (ED50 ) was 32, 62 and 55 PAC for waterhyacinth, waterlettuce and giant salvinia, respectively. Greater ED50 estimates in waterlettuce and giant salvinia were attributed to plant architecture and leaf orientation compared to waterhyacinth, which grows more vertically and has a greater overall surface area to intercept and retain spray solution. However, when treated at 100 PAC, waterhyacinth and waterlettuce resulted in 20-25% spray loss, whereas giant salvinia resulted in only 10% loss. Consequently, giant salvinia exhibited a near 1:1 relationship between spray loss and PAC (slope=-0.93). These data suggest that potential herbicide spray loss, as affected by plant density, is largely species-specific and dependent on leaf morphology and plant architecture. Further research will confirm these findings under field conditions as well as to identify other parameters that might affect spray loss when treating floating and emergent plants. © 2021 Society of Chemical Industry. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Lignin metabolism regulates lodging resistance of maize hybrids under varying planting density

Hybrids and planting density are the main factors affecting maize lodging resistance. Here, we aimed to elucidate the mechanism of the regulation of maize lodging resistance by comparing two hybrids at various planting densities from the perspective of lignin metabolism. Our results showed that compared to lodging-susceptible hybrid Xundan 20 (XD20), lodging-resistant hybrid Denghai 605 (DH605) showed a lower center of gravity and culm morphological characteristics that contributed to the higher lodging resistance of this hybrid. Lignin content, activities of key lignin synthesis-related enzymes and G-, S- and H-type monomer contents were significantly higher in hybrid DH605 than in hybrid XD20. Stalk mechanical strength, lignin accumulation and enzyme activity decreased significantly with increasing planting density in the two hybrids. While G-type monomers first decreased with increasing planting density but then remained stable, S-type monomers showed a decreasing trend, and H-type monomers showed an increasing trend. Correlation analysis showed that lodging rate was significantly correlated with plant traits and lignin metabolism. Therefore, maize hybrids characterized by high lignin accumulation, high lignin synthesis-related activities, high S-type monomer content, low center of gravity, high stem puncture strength, high cortical thickness, and small vascular bundle area are more resistant to lodging. High planting densities reduce stalk lignin accumulation, relevant enzyme activities and mechanical strength, thereby, ultimately increasing the lodging rate significantly.

Effects of plant density and nitrogen rate on cotton yield and nitrogen use in cotton stubble retaining fields

Increasing nitrogen (N) rate could accelerate the decomposition of crop residues, and then improve crop yield by increasing N availability of soil and N uptake of crops. However, it is not clear whether N rate and plant density should be modified after a long period of cotton stubble return with high N rate. This study seeks to assess the effects of N rate and plant density on cotton yield, N use efficiency, leaf senescence, soil inorganic N, and apparent N balance in cotton stubble return fields in Liaocheng, China, in 2016 and 2017. Three plant densities 5.25 (D5.25), 6.75 (D6.75) and 8.25 (D8.25) plants m−2 and five N rates 0 (N0), 105 (N105), 210 (N210), 315 (N315), and 420 (N420) kg ha−1 were investigated. Compared to the combination used by local farmers (D5.25N315), a 33.3% N reduction and a 28.6% increase in plant density (D6.75N210) can maintain high cotton yield, while a 66.7% N reduction at 6.75 plants m−2 (D6.75N105) can only achieve high yield in the first year. Biological yield increased with the increase of N rate and plant density, and the highest yield was obtained under 420 kg N ha−1 at 8.25 plants m−2 (D8.25N420) across the two years under investigation. Compared to D5.25N315, N agronomic efficiency (NAE) and N recovery efficiency (NRE) in D6.75N210 increased by 30.2 and 54.1%, respectively, and NAE and NRE in D6.75N105 increased by 104.8 and 88.1%, respectively. Soil inorganic N decreased sharply under 105 kg N ha−1, but no change was found under 210 kg N ha−1 at 6.75 plants m−2. N deficit occurred under 105 kg N ha−1, but it did not occurr under 210 kg N ha−1 at 6.75 plants m−2. Net photosynthetic rate and N concentration of leaves under N rate ranging from 210 to 420 kg ha−1 were higher than those under N rate of 0 or 105 kg N ha−1 at all three densities. The findings suggest that D6.75N210 is a superior combination in cotton stubble retaining fields in the Yellow River Valley and other areas with similar ecologies.

Boll-leaf system gas exchange and its application in the analysis of cotton photosynthetic function.

Estimating the boll development and boll yield from single-leaf photosynthesis is difficult as the source-sink relationship of cotton (Gossypium hirsutum L.) is complicated. As the boll-leaf system (BLS), which includes the main-stem leaf, sympodial leaf, and non-leaf organs, is the basic unit of the cotton source-sink relationship and yield formation, the concept of "BLS photosynthesis" is introduced in this study. We speculate that the characteristics of BLS gas exchange can more accurately reflect the photosynthetic function of the system, thus revealing the law of photosynthesis in the process of boll development. The results showed that the photosynthetic rate of single leaves measured by a BLS chamber was consistent with that measured by a standard single-leaf chamber. BLSs exhibited typical light response curves, and the shape of the curves was similar to those of single leaves. The light compensation point and respiration rate of BLSs were higher than those of single leaves, while the apparent quantum efficiency of BLSs was lower. Compared with single leaves, the duration of the photosynthetic function of BLSs was longer. Increasing plant density decreased the gas exchange rate per unit BLS more significantly under field conditions. There was a better linear correlation between the net CO2 assimilation rate, respiration rate of BLSs and boll biomass. Therefore, we think that the gas exchange of BLSs can better reveal the changes in photosynthetic function of BLSs and boll development. This provides a new basis for analyzing the mechanism and regulation of cotton yield formation.

Changes of Stem Characteristics, Senescence Indexes and Yield and Quality of Wintering Rye under Different Populations

In response to the production crisis caused by a winter feed shortage due to the rapid development of the animal husbandry industry, winter rye 001 was selected to study differences in stalk and senescence characteristics in yield formation in cold regions. Five density treatments were established in a randomized design as 225 × 104 plant·hm−2 (D1), 275 × 104 plant·hm−2 (D2), 325 × 104 plant·hm−2 (D3), 375 × 104 plant·hm−2 (D4), and 425 × 104 plant·hm−2 (D5). Stem characteristics, SOD activity, POD activity, MDA content, and differences in yield and feeding quality under different population densities were analyzed. The plant height, center of gravity, and stem basal internode length showed an increasing trend with an increase in planting density. The stem wall thickness, diameter, strength, and lodging resistance indices decreased. At 275 × 104 plants·hm−2, the rye crude protein content was the highest while neutral washing fiber and acid washing fiber were the lowest, and feed quality was the best. With an increase in density, spike number, grain number per spike, and thousand-grain weight first increased and then decreased. We concluded that the yield and feeding quality were best when the basic seedling was at 275 × 104 plants hm−2.

ФОРМУВАННЯ ПОКАЗНИКІВ СТРУКТУРИ ВРОЖАЙНОСТІ СОРГО ЗЕРНОВОГО ЗАЛЕЖНО ВІД СПОСОБУ СІВБИ НАСІННЯ ТА ГУСТОТИ СТОЯННЯ РОСЛИН У ПРАВОБЕРЕЖНОМУ ЛІСОСТЕПУ УКРАЇНИ

The article presents the results of studies of the influence of elements of cultivation technology on the yield of grain sorghum. Purpose. To investigate the influence of row spacing and plant density of sorghum plants of grain varieties Dnіprovsky 39 and Vіnets on the formation of indicators of the structure of crop yields in the conditions of the Right-Bank Forest-Steppe of Ukraine. Methods.Field, laboratory, comparative, analysis, generalizing, mathematical and statistical. Results. It has been proven that the best results in the formation of elements of the structure of the yield of grain sorghum were obtained when sowing seeds with a row spacing of 45 cm and a density of 150-200 thousand pieces/ha. With this sowing method, the panicle length was the largest and was equal to 28.5 – 29.9 cm in the Dniprovsky 39 variety and 28.3 – 28.2 cm in the Vinets variety, the panicle weight was 51.5 – 55.1 g in the Dniprovsky variety 39 and 54.8 – 55.4 g for the Vinets variety. The number of seeds in a panicle and their weight, depending on the increase in plant density from 150 to 250 thousand pieces/ha, decreased and the variety Dniprovsky 39 was from 1623 to 1592 pieces/panicle, and the grain weight per panicle was from 44.3 to 47.1 g. In the Vinets variety, the number of seeds decreased from 1536 to 1512 pieces/panicle, and their weight from 49.3 to 47.7 g. However, the weight of 1000 seeds was the highest at a plant density of 200 thousand pieces/ha and a row spacing of 45 cm and is equal to 31.2 g for the Dniprovsky 39 variety and 27.8 g for the Vinets variety. The grain yield in the same variant of the experiment is the highest and is 7.4 t/ha for the Dniprovskiy 39 variety and 5.1 t/ha for the Vinets variety. It should be noted that a decrease in the row spacing to 15 cm and an increase to 70 cm led to a decrease in these indicators. Conclusions. It has been established that the best formation of the elements of the yield structure of grain sorghum is observed when sowing seeds with a row spacing of 45 cm and a plant density of 200 thousand units/ha, which we recommend for growing this crop in the Right-Bank Forest-Steppe of Ukraine.

High plant density increases seed Bt endotoxin content in Bt transgenic cotton

Plant density is the cultivation practice usually employed to manipulate boll distribution, boll setting and yield in cotton production. In order to determine the effect of plant density on the insecticidal protein content of Bacillus thuringiensis (Bt) cotton plants, a study was conducted in Yangzhou University of China in 2015 and 2016. Five plant densities (PD1-PD5, representing 15000, 30000, 45000, 60000, and 75000 plants ha−1) were imposed on two Bt cotton cultivars, Sikang 1 (the conventional cultivar, SK-1) and Sikang 3 (the hybrid cultivar, SK-3). The boll number per plant, boll weight and boll volume all decreased as plant density increased. As plant density increased from 15000 to 75000 plants ha-1, seed Bt protein content increased, with increases of 66.5% in SK-1 and 53.4% in SK-3 at 40 days after flowering (DAF) in 2015, and 36.8% in SK-1 and 38.6% in SK-3 in 2016. Nitrogen (N) metabolism was investigated to uncover the potential mechanism. The analysis of N metabolism showed enhanced soluble protein content, glutamic-pyruvic transaminase (GPT) and glutamate oxaloacetate transaminase (GOT) activities, but reduced free amino acid content, and protease and peptidase activities with increasing plant density. At 20 DAF, the seed Bt toxin amount was positively correlated with soluble protein level, with correlation coefficients of 0.825** in SK-1 and 0.926** in SK-3 in 2015, and 0.955** in SK-1 and 0.965** in SK-3 in 2016. In contrast, the seed Bt protein level was negatively correlated with free amino acid content, with correlation coefficients of –0.983** in SK-1 and –0.974** in SK-3 in 2015, and –0.996** in SK-1 and –0.986** in SK-3 in 2016. To further confirm the relationship of Bt protein content and N metabolism, the Bt protein content was found to be positively correlated with the activities of GPT and GOT, but negatively correlated with the activities of protease and peptidase. In conclusion, our present study indicated that high plant density elevated the amount of seed Bt protein, and this increase was associated with decreased boll number per plant, boll weight and boll volume. In addition, altered N metabolism also contributed to the increased Bt protein content under high plant density.

CARACTERÍSTICAS DE SOLO E DENSIDADE DE SEMEADURA NA CULTURA DA SOJA

Sowing density of soybean and good soil fertility are essential factors for the sustainability of agricultural production. The objective was to evaluate the influence of chemical characteristics of the soil and sowing density on early growth and soybean yield components. The experiment was conducted in Laguna Caarapa, MS, in Latossol using the experimental design was randomized blocks, in a factorial project 2x3, with fator two classes of soil (fertility hight and low) and sowing density for (10, 12, 14 e 16 seeds per meter) with 4 repetitions. We analyzed the initial growth and agronomic characteristics and the soybean yield. The data were submitted to an evaluate of variance and the means compared using Tukey’s test (p ? 0,05). The survey showed no difference in soil caracteristics ans sowing density between for soybean yield. With increasing plant density ,low number of ramifications per plant and pods per plant.. The mass of a 100 grains did not vary in soquind density evaluation.

Reducing N Application by Increasing Plant Density Based on Evaluation of Root, Photosynthesis, N Accumulation and Yield of Wheat

(Aims) To clarify the mechanisms though which dense planting could alleviate the negative effect of the reducing N rate on yield, (Methods) an experiment with four nitrogen levels—0 (N0), 120 (N1), 180 (N2) and 240 (N3) kg N ha−1—and three plant densities—180 (D1), 240 (D2) and 300 (D3) × 104 basic seedlings ha−1—was conducted. (Results) Increasing plant density decreased the root length, root volume, root surface area and root tips of individual plant while it enhanced the aforementioned root traits in population. The chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate of the individual plants were decreased with the increase in plant density and enhanced with the increase in N level. The increasing density and N application rate enhanced the leaf area index, photosynthetic high-efficiency leaf area and canopy photosynthetically active radiation of population. N accumulation per plant was decreased with increasing density and was enhanced with an increasing N application level. Within the same N level, the N accumulation in the population, N production efficiency and N recovery efficiency were consistently D3 > D2 > D1. A high N application rate with high density was not conducive to improving the NR (nitrate reductase), GS (glutamine synthetase) and GOGAT (glutamate synthase) activities. The yield could be maintained as stable or improved if decreasing by 60 kg N ha−1 with increasing 60 × 104 basic seedlings ha−1 within the range of N application in this experiment. (Conclusions) These results indicated that the yield of wheat could be improved with less N application by adjusting the compensatory effects from the plant density in populations.

Improving photosynthesis to increase grain yield potential: an analysis of maize hybrids released in different years in China

In this work, we sought to understand how breeding has affected photosynthesis and to identify key photosynthetic indices that are important for increasing maize yield in the field. Our 2-year (2017–2018) field experiment used five high-yielding hybrid maize cultivars (generated in the 1970s, 2000s, and 2010s) and was conducted in the Xinjiang Autonomous Region of China. We investigated the effects of planting density on maize grain yield, photosynthetic parameters, respiration, and chlorophyll content, under three planting density regimens: 75,000, 105,000, and 135,000 plants ha−1. Our results showed that increasing planting density to the medium level (105,000 plants ha−1) significantly increased grain yield (Y) up to 20.32% compared to the low level (75,000 plants ha−1). However, further increasing planting density to 135,000 plants ha−1 did not lead to an additional increase in yield, with some cultivars actually exhibiting an opposite trend. Interestingly, no significant changes in photosynthetic rate, dark respiration, stomatal density, and aperture were observed upon increasing planting density. Moreover, our experiments revealed a positive correlation between grain yield and the net photosynthetic rate (Pn) upon the hybrid release year. Compared to other cultivars, the higher grain yield obtained in DH618 resulted from a higher 1000-kernel weight (TKW), which can be explained by a longer photosynthetic duration, a higher chlorophyll content, and a lower ratio of chlorophyll a/b. Moreover, we found that a higher leaf area per plant and the leaf area index (HI) do not necessarily result in an improvement in maize yield. Taken together, we demonstrated that higher photosynthetic capacity, longer photosynthetic duration, suitable LAI, and higher chlorophyll content with lower chlorophyll a/b ratio are important factors for obtaining high-yielding maize cultivars and can be used for the improvement of maize crop yield.

Methodology of Analyzing Maize Density Loss in Smallholder’s Fields and Potential Optimize Approach

Increasing plant density is a key measure to close the maize (Zea mays L.) yield gap and ensure food security. However, there is a large plant density difference in the fields sown by agronomists and smallholders. The primary cause of this phenomenon is the lack of an effective methodology to systematically analyze the density loss. To identify the plant density loss processes from experimental plots to smallholder fields, a research methodology was developed in this study involving a farmer survey and measurements in a smallholder field. The results showed that the sowing density difference caused by farmer decision-making and plant density losses caused by mechanical and agronomic factors explained 15.5%, 5.5% and 6.8% of the plant density difference, respectively. Changing smallholder attitudes toward the value of increasing the plant density could help reduce this density loss and increase farm yields by 12.3%. Therefore, this methodology was effective for analyzing the plant density loss, and to clarify the primary causes of sowing density differences and plant density loss. Additionally, it was beneficial to identify the priorities and stakeholders who share responsibility for reducing the density loss. The methodology has wide applicability to address the sowing density differences and plant density loss in other areas to narrow crop yield gaps and ensure food security.

Effect of foliar application of flourish microcombi complex fertilizer and plant density on yield and some quantitative traits of promising sunflower cultivars

Background and objectives: Sunflower belongs to the Astraea family and is one of the three important oil plants in the world, it has a high percentage of achene oil (45-50%). One of the main reasons for the low sunflower achene yield, is the lack of micronutrient elements. Thereforestrengthen, maintain productivity and determine the most appropriate crop density, in the new sunflower cultivars is necessary to achieve the desired yield. The present experiment was also performed basis on the selection of the most suitable promising sunflower cultivars in the best plant density and application levels of complex fertilizer flourish microcombi in Dezful city. Materials and Methods: In order evaluation of yield and some quantitative traits of promising sunflower cultivars to foliar application of microcombi complex fertilizer and interaspecific competition, An split split plot experiment in a randomized complete blocks design with three replications and three factors density as the main factor (7, 9, 11 and 13 plant/m2), complex fertilizeras the first sub-factor (0, 1 and 2 kg/ha) from the source of complex fertilizer flourish microcombi produced by Shimikord company and cultivar as a second sub-factor (Felix, Shakira, Oscar, Savana, Shams, Labad, Sudimance, Monaliza) carried out in the crop year 2018-2019 at Dezful Shahid Rajaei Company. The seeds of the tested cultivars were prepared from Shahid Rajaei Dezful Company. Each experimental plot was considered with 6 planting line to length of 1.5 m with a lines spacing of 75 cm and according to the density of 7, 9, 11 and 13 plant/m2, the plants were arranged on planting lines at intervals of 18, 15, 12 and 9 cm in the three to four leaf stage, respectively. After physiological maturation of achenes and harvesting of plants, traits stem height, stem diameter, head diameter, number of achene/head, achenes of weight/head; achene yield and oil yield were measured. Results: The results showed a significant effect of foliar application of complex fertilizeras and density on the studied traits except stem height. Shams cultivar with 198.36 cm, had the maximum stem height. According to the results, foliar application of complex fertilizeras causes increases the stem diameter, number of achene/head, achenes of weight/head and achene and oil yield (t/ha) relative to the control. Also increasing planting density, despite reducing the number and weight of achene/head, increased achene yield. With increasing density, achene yield of single plant decreased, but increasing the number of plants per unit area compensated for this decrease. According to investigation the results of comparing the means, foliar application of complex fertilizeras by improving yield components and reducing competitive stress between plants at high planting densities, cause increase achene yield in sunflower. The maximum achene and oil yield were obtained to 5.40 and 2.64 t/ha, respectively, in the density 11 plant/m2 and foliar application 1 kg/ha complex fertilizeras by Felix cultivar. The increase yield in the density of 11 plant/m2, can be the result of sunflower adaptation by increasing the plant density and shows the achene yield has changed relatively little. Oil yield depend to achene yield and oil percentage, therefore, it seems that in the present experiment, higher achene yield in the density of 11 plant/m2 and improved photosynthesis and proper achene production in the time foliar application of complex fertilizeras, caused to increase oil yield. Conclusions: Now with aware of the response of cultivars at different plant densities per unit area; it seems that the beneficial effect of foliar application of complex fertilizeras can cause reduce the damage by intraspecific competition and increase the yield of different sunflower genotypes in conditions of Dezful city and similar regions.

English

Use of optimum plant spacing (planting density) is one of the important agronomic practices to maximize the productivity of lettuce. A field experiment was conducted to assess the responses of two lettuce varieties to different plant spacing at Debrezeit and Holeta Agricultural Research Centers representing two different agro-ecologies in Ethiopia. Nine treatment combinations of three levels of inter-row and three levels of intra-row spacing were studied on two types of lettuce varieties. The treatments were arranged in a randomized complete block design (RCBD) with three replications in a factorial experiment. The results revealed that marketable and total fresh leaf yield, and fresh leaf weight per plant were significantly affected by the main effect of plant spacing and variety as well as its interaction (p<0.05). Increasing planting density increased the total fresh leaf yield per unit area in both varieties, however reduced the fresh leaf weight per plant. The highest fresh leaf yield was obtained using 40 cm x 20 cm (125000 plants ha-1) planting density from variety Great Lakes, while variety Rsk-3 recorded its highest fresh leaf yield at the highest planting density of 30 cm x 20 cm (166667 plants ha-1). Great Lakes was superior over Rsk-3 in most yield parameters studied though Rsk-3 was better in leaf dry weight percent. Besides, both varieties responded differently in both sites while Great Lakes performed better at Debrezeit than at Holeta and Rsk-3 did well at Holeta than at Debrezeit. Hence, 40 cm x 20 cm and 30 cm x 20 cm could be used as the optimum plant spacing to grow Great Lakes and Rsk-3 respectively in the respective agro-ecologies. Key words: Agronomic practices, planting density, inter-and intra-row spacing, competition.

Increasing plant density increases Bt toxin concentration of boll wall in cotton by decreasing boll setting speed

BackgroundIn order to uncover the mechanism of significantly reduced insect resistance at the late developmental stage in cotton (Gossypium hirsutum L.), the relationship between boll setting rate under different planting densities and Bacillus thuringiensis (Bt) insecticidal concentrations in the boll wall were investigated in the present study. Two studies were arranged at Yangzhou, China during the 2017–2018 cotton growth seasons. Five planting densities (15 000, 25 000, 45 000, 60 000 and 75 000 plants per hectare) and the flower-removal treatment were imposed separately on Bt cotton cultivar Sikang3 to arrange different boll setting rates, and the boll setting rates and Bt toxin content were compared.ResultsHigher boll setting rate together with lower Bt toxin contents in boll wall was observed under low planting density, whereas lower boll setting rate and higher Bt toxin contents were found under high planting density. Also, higher Bt protein concentration was associated with higher soluble protein content, glutamic-pyruvic transaminase (GPT), and glutamic oxaloacetate transaminase (GOT) activities, but lower amino acid content, and protease and peptidase activities. It was further confirmed that a higher boll setting rate with lower Bt protein content under flower-removal.ConclusionsThis study demonstrated that the insecticidal efficacy of boll walls was significantly impacted by boll formation. Reduced protein synthesis and enhanced protein degradation were related to the reduced Bt toxin concentration.

Weed Management Practices to Improve Establishment of Selected Lignocellulosic Crops

Lignocellulosic biomass is one of the dominant renewable energy resources suited for the production of sustainable biofuels and other energy purposes. This study was focused on weed management strategies that can improve the establishment of six lignocellulosic crops. The studied crops included: giant miscanthus, switchgrass, giant reed, cardoon, sweet sorghum, and kenaf. Delayed planting, increased planting densities, and mulching techniques can suppress weeds in giant miscanthus. Weed competition is detrimental for switchgrass establishment. Seedbed preparation and cultivar selection can determine its ability to compete with weeds. Giant reed is unlikely to get outcompeted by weeds, and any weed control operation is required only for the first growing season. Competitive cultivars and increased seeding rates maximize the competitiveness of cardoon against weeds. Several cultural practices can be used for non-chemical weed management in sweet sorghum and kenaf. For all crops, pre-emergence herbicides can be applied. The available safe post-emergence herbicides are limited. Mechanical weed control during crucial growth stages can provide solutions for sweet sorghum, kenaf, and perennial grasses. Further research is required to develop effective weed management strategies, with emphasis on cultural practices, that can improve the establishment of these prominent lignocellulosic crops.

Reduced row spacing improved yield by optimizing root distribution in maize

Roots play major roles in plant anchorage, water and nutrient uptake, crop growth and yield. Knowledge regarding yield responses to root spatial distribution is still limited in maize. Here we designed three plant densities in the tube and in the field, respectively. The tube study included plant densities of 1, 2, and 3 plants tube–1 and field study included 50025 (D50025), 67500 (D67500), and 100050 (D100050) plants ha–1, with two row spacings in D50025 (60 and 80 cm), three row spacings in D67500 (40, 60, and 80 cm), and two row spacings in D100050 (40 and 60 cm). With increased plant density and decreased row spacing grain yield improved, but root size and root biomass per plant decreased. Root dry weight per plant increased by 25–32 % at D50025 and decreased by 29–38 % at D100050 compared to D67500. Horizontally, reducing row spacing increased inner roots and reduced outer roots. There were significant correlations of yield with inner (R2 = 0.603** for D67500) and outer (R2 = −0.544* for D67500) root dry matter. Vertically, reducing row spacing increased root dry weight and most of the roots were distributed in the top 0–10 cm soil layer. Overall, high plant density inhibited root growth, but narrow row spacing compensated this inhibition to some extent by optimizing root distribution, thus increasing grain yield. Horizontal root distribution had a greater effect on grain yield than vertical distribution under high density condition, which alleviated inter-plant root competition and increased yield.

Increasing plant density improves grain yield, protein quality and nitrogen agronomic efficiency of soft wheat cultivars with reduced nitrogen rate

Application of nitrogen (N) fertilizer usually increases grain yield (GY) and grain protein content (GPC) simultaneously. But low GPC is desirable in soft wheat (Triticum aestivum L.). To break the unexpected link, we investigated the combined effects of reduced N rate, increased plant density on GY, nitrogen agronomic efficiency (NAE) and GPC targeting biscuit-making of two soft wheat cultivars. The field experiments involved four N rates (240, 180, 120 and 0 kg N ha−1) and three plant densities (180, 240 and 300 × 104 plants ha−1). Reducing N rate improved grain quality for biscuit-making and NAE in soft wheat, but resulted in lower dry matter accumulation and caused a significant GY loss. With the N rate ranged from 240 to 0 kg N ha−1, GY loss of 16.28–18.54 kg ha−1 was observed for every 1 kg N ha−1 reduction. Increasing plant density significantly enhanced the population dry matter accumulation and partially compensated for GY loss caused by reduced N via increasing the number of effective ears, meanwhile further improved grain quality and NAE. When the plant density increased from 180 to 300 × 104 plants ha–1, increasing 1.0 × 104 plants ha–1 led to an increment in average GY of 4.79, 6.78 and 3.98 kg ha–1 under 180, 120 and 0 kg N ha−1, respectively. The reduction of 1 kg N ha–1 was replaced by increasing app. 2.40–4.09 × 104 plants ha–1 to maintain same GY. The decrease in GPC by the combination of reduced N rate and increased plant density was mainly attributed to the variations in pre-anthesis accumulated N in vegetative organs as well as the whole plant. Moreover, reducing N rate showed a more remarkable effect on GPC than increasing plant density, and their interaction effect was significant. Our study therefore provided an agronomic approach to balance GY and GPC targeting biscuit-making in soft wheat production by the combination of low N rate and high plant density.

Optimizing irrigation and planting density of spring maize under mulch drip irrigation system in the arid region of Northwest China

Abstract The limited availability of water resources severely restricts agricultural development in the semiarid and arid regions of Northwest China. A two-year field experiment was conducted to investigate the effects of irrigation and planting density on the soil water content (SWC), growth and development, yield, water use efficiency (WUE) and economic benefits of spring maize in arid areas under mulch drip irrigation system. The optimized combination of irrigation and planting densities for high grain yield, WUE and net return were obtained by multiple regression analysis. Experiment included three irrigation treatments (HI: 450 mm; MI: 337.5 mm; LI: 225 mm) and four planting densities (D1: 75,000 plants ha−1; D2: 90,000 plants ha−1; D3: 105,000 plants ha−1; D4: 120,000 plants ha−1). The results showed that the reduction of irrigation decreased SWC, leaf area index (LAI), aboveground biomass, yield and evapotranspiration (ET), but improved WUE. HI and MI were significantly different from LI. Increasing planting density increased LAI and ET, but reduced SWC and aboveground biomass. Planting density had significant effects on yield and WUE, which differed in both years. The overall yield, WUE and net return were greater than the two-year average of HI-D1 under an irrigation amount of 271.9–500.2 mm and a planting density range of 7.1–14.3 × 104 plants ha-1. MI-D2, with 25 % reduced irrigation, increased the two-year average yield, WUE and net return by 5.2 %, 20.2 % and 27.2 %, respectively, compared to HI-D1. Therefore, irrigation of 337.5 mm at a medium planting density of 90,000 plants ha-1 under mulch drip irrigation is recommended for spring maize production in the drylands of Northwest China in our research.